The Incurable Matchmaker

Signet Regency, 1990, ISBN 0-451-16541-1

Diana Ingram is as virtuous as she is beautiful. The Marquess of Kenwood is
handsome and charming--and a notorious libertine. There can be no question
of any connection between the two--until Kenwood's envious friends and
acquaintances goad him into wagering that he can seduce Mrs. Ingram within a
month.